Cancer cells can migrate from a primary tumor site in a body into proximal and distant tissues where they can form metastases. The migration of the cancer cells can occur along preexisting paths in the body, such as blood or lymphatic vessels, collagen fibers, white matter tracts, or vessels for peritoneal fluid flow. Observing and quantifying the cancer cell migration processes in vivo is difficult, in part due to the natural variability and complexity of the microenvironment experienced by the moving cells and by the close interaction with other cells.
One difficulty in studying cancer cell migration is the variety of the processes involved in cell migration. Cancer cell migration is the cumulative outcome of at least four basic cellular processes that include cellular motility, invasion of the extracellular matrix (ECM), adhesion to substrates, and cell-cell communication. In addition, very low numbers of cancer cells are typically recovered from patients (e.g, a few hundred cells). Method and assays for identifying motile cancer cells in a small cancer cell population (e.g., fewer than about 103 cells) can be useful, for example, in identifying potentially migratory metastatic cancer cell populations. In addition, such methods and assays can be useful to identify chemical agents that inhibit the migration of cancer cells.